This relates generally to electronic devices with displays and, more particularly, circuitry for displays such as organic-light-emitting diode displays.
Electronic devices often include displays. For example, cellular telephones and portable computers include displays for presenting information to users.
Displays such as organic light-emitting diode displays have an array of display pixels based on light-emitting diodes. In this type of display, each display pixel includes a light-emitting diode and thin-film transistors for controlling application of a signal to the light-emitting diode to produce light.
Variations in transistor threshold voltages and other characteristics can lead to undesired visible display artifacts. Threshold voltage compensation circuitry may be used to compensate for threshold voltage variations and thereby enhance display performance. Threshold voltage compensation circuitry includes thin-film transistors and capacitors. If care is not taken, the structures used to implement capacitors and other devices in threshold voltage compensation circuitry and other display circuitry can adversely affect device performance. For example, if a storage capacitor in a threshold voltage compensation circuit exhibits a capacitance value that is too small, leakage currents may dissipate stored charges prematurely. If the storage capacitor consumes excessive circuit real estate, it may not be possible to achieve a desired pixel pitch in a display.
It would therefore be desirable to be able to provide improved threshold voltage compensation circuit capacitors and other structures for use in display circuitry in an organic light-emitting diode display.